2
dc1988af
DEMO MANUAL DC1988A
Quick start proceDure
Demo circuit 1988A is easy to set up to evaluate the per-
formance of the LTM8058. Refer to Figure 4 for proper
measurement equipment setup and follow the procedure
below:
NOTE. When measuring the input or output voltage ripple,
care must be taken to avoid a long ground lead on the
oscilloscope probe. Measure the input or output voltage
ripple by touching the probe tip directly across the V
IN
or
V
OUT
and GND terminals. See Figure 5 for proper scope
probe technique.
1. With power off, connect the input power supply to V
IN
and GND.
2. Turn on the power at the input.
NOTE. Make sure that the input voltage does not exceed 30V.
3. Check for the proper output voltages. (For V
OUT1
, check
the voltage between V
OUT1
and V
OUT
–
. For V
OUT2
, check
the voltage between V
OUT2
and V
OUT
–
.)
NOTE. If there is no output, temporarily disconnect the
load to make sure that the load is not set too high.
4. Once the proper output voltages are established, adjust
the load within the operating range and observe the
output voltage regulation, ripple voltage, efficiency and
other parameters.
Figure 1. V
OUT1
Typical Maximum Output
Current vs V
IN
with V
OUT2
Unloaded
Figure 2. V
OUT1
Output Noise Spectrum with I
OUT1
at 100mA and V
IN
at 12V (V
OUT2
Has No Extra Load)
Figure 3. V
OUT2
Output Noise Spectrum with I
OUT2
at 100mA and V
IN
at 12V (V
OUT1
Has No Extra Load)
V
IN
(V)
4
0
OUTPUT CURRENT (mA)
300
250
200
150
100
50
400
350
6
22 24 26 28 30
8 10 12
18
16
14
dc1988a F01
20
FREQUENCY (MHz)
0
–90
INTENSIT
Y (dBm)
–20
–30
–40
–50
–60
–70
–80
0
–10
3.5 4 4.5 5
0.5 1
2.5
2
1.5
dc1988a F02
3
FREQUENCY (MHz)
0
–90
INTENSIT
Y (dBm)
–20
–30
–40
–50
–60
–70
–80
0
–10
3.5 4 4.5 5
0.5 1
2.5
2
1.5
dc1988a F03
3